This invention concerns auto safety systems and more particularly inflatable cushion devices commonly referred to as "air bags". In such devices, a fabric cushion (the air bag) is stored in a folded condition within a receptacle defining a storage space within the vehicle passenger compartment. Upon activation of a crash sensor detecting an imminent high velocity impact, the air bag is inflated with a chemically generated gas and deployed in a manner and position calculated to absorb the impact of the driver or passenger thrown forward as the vehicle is sharply decelerated at impact.
The folded air bag, gas generator, and other components of the system may be stored within a receptacle mounted in the steering wheel or behind the instrument panel forward of the passenger seat, covered by one or more doors which are opened by pressure generated by the inflating air bag.
The receptacle must be stored in a manner which is tamper-proof, yet allowing instantaneous deployment of the air bag upon system activation. Further, the covering must resist normal pressure exerted thereon as by incidental contact with the vehicle occupants.
Prior art systems have typically involved exteriorly visible patterns on the surface instrument panel or steering wheel covers delineating the openings therein through which the air bag will be deployed.
The presence of the visible pattern reduces the aesthetic appeal of the interior trim surfaces and is disturbing to many persons as it makes the presence and possible pending deployment of the air bag obvious. This visible pattern also makes the system more vulnerable to tampering because of its evident location.
The usual approach in designing a closure is to provide a hinged door latched by a detent mechanism or snap fitted portions forced apart by the pressure of the inflating air bag. See U.S. Pat. No. 4,327,937 issued on May 4, 1982 on a "Downwardly Foldable Covering For a Gas Cushion" for an example of such a covering.
Another common approach is to provide an exteriorly visible line of weakening in a covering skin which is ruptured by the air bag upon deployment. See for examples of such a design U.S. Pat. No. 4,400,010 issued on Aug. 23, 1983 for "Air Bags in Motor Vehicles", and U.S. Pat. No. 4,334,699 issued on Jun. 15, 1982 for "Cap Like Cover for an Air Bag Installation".
U.S. Pat. No. 3,640,546 issued on Feb. 8, 1972 for a "Safety Apparatus" discloses a preweakened covering skin over closure doors but the seam skin is unsupported along the seam, and thus the seam would be tactilely perceptible and also, over time, would also become visible due to the absence of any support underneath.
Another approach is described in U.S. Pat. No. 3,632,136 issued on Jan. 4, 1972 for a "Safety Apparatus", in which a powerful linear shaped explosive charge is used to sever a door lock and reinforcing panel to release a locked door just prior to deployment of the air bag to enable the door to be pushed open by the air bag.
In all of the above designs, the outline of the closure is suggested, and some also result in the showering of debris into the passenger compartment when the system is activated.
Most designs also use separately manufactured and installed covering doors, which increases the cost of manufacture of the air bag installation.
In copending U.S. patent application Ser. No. 07/303,132 filed on Jan. 30, 1989 U.S. Pat. No. 5,080,393 there is disclosed an invisible closure utilizing a length of detonation cord to create an air bag deployment opening in an interior auto body panel to avoid any suggestion that an air bag is installed therein.